1. Field of the Invention
The invention relates to rotary switches. In one aspect, the invention relates to a rotary switch having a plurality of rotary switch positions that mimic a keystroke from a momentary pushbutton keyswitch. In another aspect, the invention relates to a logic control cycle for a rotary switch for ensuring that a change in circuit conditions from the operation of the rotary switch is properly interpreted as a selected keystroke. In yet another aspect, the invention relates to rotary switches that can be used with a switch array.
2. Description of the Related Art
An array of momentary push-button keyswitches is frequently used in consumer appliances, such as dishwashers, to select particular functions, such as a standard wash cycle, a heavy-duty wash cycle, or a rinse cycle. The push-buttons are mechanically biased into an off/open position. Momentarily depressing the keyswitch closes a circuit, permitting the sending of a signal to a controller. The controller interprets the signal to select a function to activate.
The array of momentary push-button keyswitches typically utilizes a matrix of associated “send” and “receive” electrical lead lines or electrodes that intersect and have their ends connected to the controller. The momentary push-button keyswitches are located at the intersection of the send and receive lines. Depressing a selected push-button keyswitch closes the connection for the corresponding intersecting pair of “send” and “receive” lines to permit the transmission of a signal through the temporary circuit. In most configurations, the intersections of the send and receive lead lines do not literally intersect. Instead the leads lines extend to the momentary push-button switch lying at what would be the point of intersection. Depending on the type of circuit, the send and receive lead lines can overlie each other at different layers in the circuit board and the momentary push-button switches connect the send and receive lead lines at the overlapping zone.
To determine which switch has been selected/depressed, the controller polls the matrix by sequentially sending an electrical signal or “pulse” through each selected “send” line. While sending the electrical signal down a selected send line, the controller then sequentially “samples” the “receive” lines for a return signal. If a return signal is detected on a “receive” line, the controller identifies which push-button has been depressed by its location in the matrix based on the corresponding send and receive lines, and thereby activates the particular function associated with the selected push-button. The total time to signal and sample the entire matrix is typically on the order of a few milliseconds, a time interval much shorter than the time taken by a typical consumer to depress a selected function button. Thus, when a consumer depresses a particular function button, the controller will have signaled and sampled the matrix to identify the selected button.
Upon release by the user, the momentary push-button keyswitches return to the off/open position, thereby opening the connection between the “send” and “receive” line. Indeed, the control assembly is typically designed so that the controller is properly actuated by a momentary connection of the “send” and “receive” lines such as occurs with a momentary push-button keyswitch.
The advantage of a switch array is that multiple switches can use the same send/receive lines thereby reducing the lead line requirements as compared to each switch having its own dedicated lead lines. The structure also permits a greater density of switches to be placed on a printed circuit board as compared to each switch having its own dedicated lead lines. However, for the switch array to provide these benefits and advantages, it is important that the switches rest state be in an open position so they do not short the array.
While switch arrays using momentary push-buttons are very useful, they are incompatible with switching devices that remain in the closed position during their rest state. Most notably, the common rotary switch is such a switch that historically has been constructed to remain in the closed position as its steady state. In other words, rotary switches are typically designed for connecting a “send” and “receive” line in order to enable a continuous, rather than momentary, signal to be sent through the switch, thus rendering the rotary switch incompatible with the send and receive line array designed for momentary switches.
The selection between momentary push-buttons and a rotary switch is often a design choice. In some instances, the use of a rotary switch may be a matter of personal preference for a particular user. Some users may find that a rotary switch is intuitively more appropriate for certain switching functions. A rotary switch may be easier to operate for some users.
It is desirable to have rotary switches and momentary push-button arrays that are interchangeable so that either switch could be used. The interchangeability of rotary switches and momentary push-button arrays would provide appliance control designers with greater flexibility. It would also make possible the consumer being able to select their preferred switch.